Slide-actuated firearm with tilting locking block



L. R. CRITTENDON ET AL 2,645,873

July 21, 1953 SLIDE-ACTUATED FIREARM WITH TILTING LOCKING BLOCK Filed Jan. 51, 1950 3 Sheets-Sheet l INVENTORS N m m. 5 $4 n m O m. R u H m LPAUWMU Y B July 1, 3 L. R. CRITTENDON ET AL 2,645,873

SLIDE-ACTUATED FIREARM WITH TIL-TING LOCKING BLOCK 3 Sheets-Sheet 2 ATTORNEYS INVENTORS PHIL/P 1?. HAS/(EL L Filed Jan. 31, 195Q INVENTORS A Tram 5Y8 y 1, 1953 L. R. CRITTENDON ETAL 45,873

SLIDE-ACTUATED FIREARM WITH TILTING LOCKING BLOCK Filed Jan. 31, 1950 3 Sheets-Sheet 3 AEX/E' 1?. C/e/rrsA/oon/ y PH/L IF A. H4 S/ffLL Patented July 21, 1953 SLIDE-ACTUATED FIREARM WITH TILTING LOCKING BLOCK Lexie R. Crittendon and Philip R. Haskell, Ilin,

N. Y., assig'nors to'Remington-Arms Company, Inc., Bridgeport, Conn, a corporation of Delaware Application'January s1, 1950,'Serial'No. 141,532

. 1 This invention relates to improved breech loading firearms and finds its widest application in the type commonly identified as forearm slide actuated. The invention is illustrated by a showing of a shotgun of that type, although obviously certain principles of the design could be applied with equal utility to center-fire rifles. Although the widest application of the invention is in the forearm slide actuated field, some of the elements thereof, for example, the breech locking mechanism, could be applied with great utility to straight pull actuated or autoloading designs, either gas or recoil operated.

The principal object of this invention is the production of a firearm action which may be operated smoothly and with certainty that it will be free from malfunctions. It is a basic requirement that this object be achieved without in any way sacrificing existing standards of safety and fine appearance.

A further object is the production of a firearm which can be manufactured with greater economy and one which utilizes to the greatest extent parts and tooling which are interchangeable throughout a series of gauges and with companion models.

It is contemplated that these objectives can be best achieved by employing a construction in which barrel and breech bolt are locked to each other during firing through the agency of a barrel extension and a locking block which engages between cooperating surfaces on the breech bolt and barrel extension. A breech bolt slide may be provided to carry the breech bolt and actuate the a locking block, the slide itself being suitably guided for reciprocation in the gun receiver. The'slide may conveniently be arranged to be directly actuated by a straight pull handle thereon, may be actuated by action bars extending to a manually operated slidable forearm, or to a suitable gas piston and spring assembly. In addition, without modification of the locking mechanism per se, a breech bolt return spring may be coupled to the slide and the barrel permitted to recoil as in certain well-known autoloading shotgun designs of the type first developed by the great John M. Browning. Accordingly, where the term actuator is used hereinafter and in the claims, it should be understood to refer interchangeably to a handle, slidable forearm, gas piston, or other means to actuate the breech bolt slide as discussed above.

The exact nature of the invention as well as other objects and advantages thereof will become apparent from consideration of the detailed spec- Claims. (01. 42 21) ification referring to the accompanying drawings,

in which:

Fig. 1 is a vertical, longitudinal sectional view of a firearm constructed in accordance with this invention. The mechanism is shown in hammer cocked, breech locked position.

Fig. 2 is a similar view with the parts in the position they would'occupy just after firing. The hammer is down and the action 'just unlocked.

Fig. S'is a similar 'view with the action completely open. In this view, the trigger plate assembly is shown in elevation to illustrate the action of the carrier and carrier dog.

Fig. 4 is a view similar to Fig. 3, during the action closing portion of the cycle. The hammer is cocked and the shell carrier is just about to be returned to its normal lower position.

Fig. 5 is a partial longitudinal horizontal sec-- tional View taken on the line 5-5 of Fig. 1'.

Fig. 6 is a view similar to Fig. 5 taken on the line e a cf Fig. 2.

Fig. 7 is a view similar to Fig. 5 taken on the line 1-1 of Fig. 3. c

Fig; 8 is a View similarto Fig. 5 taken on the line 88 of Fig. 4.

' Fig. 9 isa cross-sectional of Fig. 1'. i

Fig. 10 is a partial longitudinal, horizontal sectional view' on the line l0'l0 of Fig. 3.

Referring to the drawings by characters of reference, it will be seen that the illustrated shotgun comprises a receiver I having a counterbore 2 in which there is received a barrel extension 3 secured to or integral with a barrel 4. A magazine tube 5 extends intothe receiver'in axial parallelism with the barrel and is rigidly secured to the receiver, as by a furnace or induction brazing operation. The magazine tube houses the usual magazine follower 6 and follower spring 1, the latter abutting at its forward end against a magazine spring retainer 8. A barrel guide ring 9 is secured to the barrel 4 in position to embrace the forward end of the magazine tube when the barrel extension is seated in the receiver. Assembly of the barrel to the receiver may be maintained by the magazine cap I!) which threadably engages the'magazinetube and bears against the forward face of the barrel guide'ringt. The cap is releasably retained in positioni by a detent plunger II and spring [2 housed in the barrel guide ring and engageable with suitable notches l3 in the rear face of the magazine cap.

A fore-end I4 is secured on a sleeve 15 between an abutment l6 and the nut I! to provide a hand grip for operatingthe action. Secured to the view on the line 99 pin retracting spring Breech looking action The upper surface at the. rear end of each action bar is cut away to interengage with'notched laterally projecting guide ribs 20 and 2| formed integrally with the breech bolt slide 22.. These guide ribs are received, with, thelactionbars,v in; the guide tracks l8a and l9a' in the-receiver and constrain the slide 22 to straight reciprocating movement within the receiver. A. generally rectangular lug 23 formed on the slide is received in an aperture 24 in the body of the breech bolt 25. This lug fits closely within the aperture in a lateral direction and. limited longitudinal movement of the lug within the aperture'is'. permitted. By this means, thebreech bolt, which isof a shape. complementary to the inside. of the receiver above. the. uide tracks [8a and. lad, is also constrained to straight fore and, aft movement in the receiver.

. The slide aperture 24 also receives the locking block 26- which is formed to define on its lower surface a breech locking cam 21 and a breech unlocking cam 28', both of which cooperate with the slide lug 23. As will be noted from Fig. 9, the locking block is of inverted U-shaped crosssection and straddles the firing pin 29 and firing the block is formed to define a locking lug 3| which engages a locking recess 32 in the barrel extension. Therear end of the upper surface of the locking block is, relieved at 33 to permit the locking, block to turn about an imaginary center under the urging of either of the cams 2.1 or. 2.8 without allowing the locking block to bind or rattle in the receiver.

It will be noted that theupper surf-ace 'of 'the slide lug 23 is raised somewhat at the front end and that the locking .block is more deeply indented on its lower surface immediately to the rear of the locking cam 21. This lack of symmetry is deliberately introduced to make it impossible to assemble the gun with the locking blockin reversed position. 7

As will be noted in Fig. l, theslide lug 23 has been drawn forward by the action bars .completely past the locking cam 21 and is fully beneath the front end of the locking block securely holding the lug 3| in the recess 32. The forces incident to the explosion of a chambered shell are transmitted through the breech bolt to the front face of the locking block and through the locking block to the barrel extension. As long as the action bars are in their fully forward position, the breech block will be locked to the barrel extension and only a small percentage of the locking loads due directly to gas pressure in the barrel will be shared with the receiver. Since the receiver serves mainly to guide the parts and to transmit recoil forces to the buttstock, the receiver design or material specification is not particularly critical and a light weight-action is possible without sacrificing safety or durability.

As shown in Fig. 2, the fore-end and action bars may be drawn rearwardly after firing, disengaging the lug 23 on the slide from the breech locking cam 2-1 and immediately thereafter engaging theunlocking cam 28. This, operation Theupper surface of support rivet. 40 secures the ejector 4|.

4 causes the locking block to turn about a fulcrum in contact with the top of the receiver and disengages the locking lu-g from the recess in the barrel extension. After the locking block has reached its fully unlocked position, the lug 23 on the slide contacts the rearend of-the aperture 24 in the breech bolt and thereafter carries the breech bolt with it to the position shown in Fig. 3.

Figmlshows the. mechanism during the closing stroke of the breechbolt and it will be noted that,

although the slide lug is engaging the breech locking'cam.v on. the, locking block, the locking lug simply slidesalong the smooth top of the receiver and barrel extension until the breech bolt reaches its foremost position. At that point, the

locking lug swings. into the recess in the barrel extension and the slide lug moves in completely beneath the front end of the locking block to retain it in locked position. An action bar lock 34, actuated. by meansv to belater described, is provided to engage the rearendof the left hand action barto: retain. the mechanism locked. until the; shell has been fired or the action bar lock manually released. 7

As a safety feature, thehead of the firing pin 29 is enlarged and cooperates with buttresses 35 formed in the walls of. the slot in the locking block to insure that the firing pin cannot be causedito protrude from the face of the breech bolt unless: or until the breech bolt is securely locked to the barrel extension. In addition to the safety function of preventing firing from an unlocked breech, this action positively retracts thefiring pin, in case the retracting spring has failed to accomplish its function, and thus avoids any change that a protruding'firing pin might interfere with ejection.

Extraction. and ejection The. breech bolt isv provided at the right hand edge of the breech face with the usual springloaded extractor 36 which engages the rim of. a chambered shell and withdraws it as the bolt is moved to the rear. An ejector support 31 is rivetedto the side wall of the receiver and pro- .vided with a tongue 38 engageable with a slot 39 in the rearend of the barrel extension to act as a locating key therefor. A secondary riveting operation on. the head of the foremost ejector The ejector is unique in that it consists of a relatively light leaf spring member, free at its rear end and so formed as to normally project into the receiver at an angleto the wall thereof. Near the rear extremity of the ejector, a sharp bend therein defines an ejector abutment 42. As the shell is drawn rearwardly, the spring ejector holds it over in secure engagement with the extractor hook. When the shell head impinges on the abutment 42, the shell pivots about the extractor claw and flips to the side out of the ejection port. It is desirable to position the abutment 42 in such a location that the open mouth of the shell undergoes a slight interference with 'thefront edge of the ejection port. This interference produces a detent action, permitting more force to be stored-in the'spring ejector before complete release'and otherwise assists in controlling ejection. Primarily, the spring action cushions the initial application of the ejecting force and the resilient followthrough permitted. by the free rear end provides asmoother and more consistent ejection.

Shell feeding As in the usual repeating shotgun, shells are retained in a magazine 5 under the urging 'of a follower 6 and spring I and fed therefrom to the chamber as needed to replace shells fired therein. The release of shells from the magazine is under the control of a right hand shell latch 43 and a left hand shell latch 44, and these latches are, in turn, controlled by the right and left hand action bars, respectively, 18 and I9.

The shell latches 43 and 44 are each a generally fiat spring member received in corresponding longitudinal grooves in the side of the re ceiver in substantial opposition to the edges of a horizontal plane including the diameter of the magazine tube. At the rear end of the shell latches, the edges of the grooves are deformed by a staking operation to temporarily retain the latches during assembly. After assembly, they are confined in their grooves in the receiver walls by the triggerplate :35 which has a tight fit between the receiver walls and is secured therein by a front trigger plate pin 46 and a rear trigger plate pin 41. The spring action of the shell latches is such that they normally extend into the receiver in position to block the escape of shells from the magazine tube. The right hand shell latch is provided with an upwardly extending cam lug 48 and a similar lug 49 is provided on the left hand shell latch. Each of these lugs extends into the track occupied by its respective action bar in position to be controlled by the cam surfaces and clearance cuts in the lower edge of the action bars. Figs. 1 through 4 show the left hand action bar H! in elevation with the lower edge cut away at 50 to permit the left hand shell latch 44 to extend into shell stopping position. A cam surface 5| is provided and cooperates with the cam lug 49 to withdraw the left hand shell latch just prior to the time the breech bolt and action bars reach their rearmost position in the receiver. Figs. 5 through 8 show the operation of the shell latches and correspond directly to Figs. lthrough 4. From these figures, it can be seen that the left hand shell latch is in shell stopping position during all portionsv of the cycle except while the action is completely open.

Although the right hand shell latch 43 is not shown in elevation, it is formed the same way as the left hand latch except for the different position of the cut-away portion 52 and cam 53. These elements are indicated by dotted lines on Figs. 5 through 8 and from consideration of these figures, it ,will be seen that the right hand shell latch 43is held in an inactive position when the action is locked and remains inactive except during a time interval somewhat longer than that in which the left hand latch is inactive. At least one of the shell latches is always in active position to prevent uncontrolled release of shells. It will be further noted that the left hand latch is positioned so that its active front edge is somewhat further from the mouth of the magazine than the front edge of the right hand latch.

Reviewing the action of the shell latches, it will be seen that the left hand latch is active and holding a shell in the magazine when the breech is completely closed, as in Fig. 5. As the 1 action is opened, the right hand action bar presents its cut-away portion opposite the cam lug 48 and the right hand latch moves into active position, as shown in Fig. 6. However, .by reason of the difierence in the fore and aft. position of the latches, the right hand la-tch'is forward of the rim of the shell, then retained by the left hand latch, and cannot influence the motion of that shell. As the action reaches very nearly the maximum breech opening, the cam 5| on the left hand action bar engages the cam lug 49 and moves the left hand shell latch to inactive position, as shown in Fig. '7, releasing the rearmost shell to spring rearwardly into position to be raised into the action. At the same time, the right hand latch catches the succeeding shell. As the action is closed, the released shell is aligned with the chamber by means to be presently described and inserted thereinto by the breech bolt. As the cut-away portion 50 of the left hand action bar comes opposite the cam lug t9, the left hand latch returns to active position, as shown in Fig. 8. Shortly before the action reaches its fully closed position, the cam 53 engages the cam latch 38, releasing the right hand latch and permitting the shell to move rearwardly into engagement with the left hand latch, as again shown in Fig. 5.

. The shell released from the magazine when the action is open is raised into position in front of the breech bolt by a carrier 5%, pivotally mounted on the trigger plate t5 by means including a carrier pivot tube 55 through which the front trigger plate pin 46 extends in securing the trigger plate. This carrier is generally similar to those employed in Browning Patents Nos. 659,507, 689,283, and 710,094. Like the constructions shown in those patents, the carrier extends rearwardly behind the pivot and there furnishes pivotal support for a carrier dog 56. A carrier dog spring 57 and plunger 58 are received in a bore in the trigger plate and act on the carrier dog, urging the dog to swing clockwise on its pivot to a position at substantially right angles to the carrier and after contacting the stop shoulder 59 to swing the carrier to a normal downward position. When shells are to be loaded into the magazine, the carrier may be raised against the spring 5'! and the curved lower face thereof serves as a loading ramp directing a shell into the magazine tube where it is retained by the left hand shell latch 44. The upper face of the carrier dog is formed to define a heel 66 and a toe 6!. As the breech bolt slide 22 rides thereover when the bolt is retracted, the carrier dog, as shown in Fig. 8, is forced to turn counterclockwise, compressing the carrier dog spring and through a leverage action, acting to hold the carrier in its lowermost position. A notch 62 in the lower face of the slide catches the heel 60 of the carrier dog as the breech bolt and slide are moved forwardly. During this forward movement, the carrier dog acts as a strut between the slide and the rear end of the carrier, with the inevitable result that the front end of the carrier moves up to position the shell'previously released by shell latch 44 in front of the breech bolt. During this movement, control of the shell is rendered more certain by the provision of a finger 63 on the right hand edge of the carrier. In certain positions, particularly when single loading through the ejection port and operating the action slowly, this finger may prevent dropping a shell through the ejection port. As the breech closingportion of the operating cycle reaches the point shown in Fig. 4, it will be' noted that the toe 6! of the carrier dog is working against the bottom face of the breech slide and that only a little more movement will result in prying the heel of the carrier dog out of the notch 62 and releasing the carrier to return under springurging to its. normal lower position. With the action in completely closed position, a slot 64 in the breech bolt. slide and an aligned recess in the bottom face of the bolt receive the finger 63 to permit the carrier to be displaced upwardly for loading shells into the magazine, as previously described.

Fire control The fire control assembly for this gun is, in most respects, identical in parts and in operation with the mechanism shown in the copending application of L. R. Crittendon, Serial No. 79,368, filedMarch 3, 1949, now Patent No. 2,570,772, issued October 9, 1951. In this case, the only substantial change has been to make the action bar lock 34 integral with the disconnector B5 and to provide an action bar lock finger piece 66 extending through a slot in the bottomof the trigger plate. 45. Both types of fire control are claimed in the copending Crittendonapplication, Serial No. 2%,706, filed January 6, 1951, which isa-continuation-in-part of application Serial No.'

79,368, now Patent No. 2,570,772, above noted.

To briefiy review the operation of these fire controls and thus minimize the need for reference to the above-identified copendin applications, it may be pointed out that the trigger 61 is pivotally mounted in the trigger plate 45 and provided at. a point above its pivotal mounting with means. arranged to pivotally receivea connector assembly 68 comprising a right hand connector arm 69 and a left hand connector arm 7.0, both extending in a generally forward direction. When assembled to the trigger, these arms act. as aunit. A sear H is also pivotally mounted in.th'e trigger plate and at its upper end engages a' compression spring 12 which acts at its rear end upon the connector assembly. This spring thus: serves to urge the upper end of the sear forwardly and the upper end of the trigger rearwardly while simultaneously urging the arms of the connector to swing downwardly. The upper end of the sear is also formed to define a. hammer hook 73 which is adapted to engage the hammer T5 at notch 75a and thereby to releasably retain the hammer in cocked position. The right hand connector arm 69 is arranged to acton a step. 14 on the sear and, when the trigger is pulled, will urge the sear to swing upon its pivot and release the hammer 15.. A clearance recess 1 la is also formed in the sear adjacent the step 74 to receive the end of the arm 69 and to permit the. trigger to beheld back without effect upon the sear. The connector may be moved to this inactive position by means of a disconnector 65 which is pivotally mounted near the forward end of the trigger plate and engages beneath the forward end of the left hand connector arm it. The disconnector may be actuated manually by means of depression of the action bar lock finger piece 66 which, at the same time, operates the'action bar lock 34, permitting the action bars to be drawn rearwardly, unlocking the action. The disconnector is also operated as a function of the fall of the hammer 15 by means which include a short arm 16 on the disconnector positioned'in the path of the hammer spring plunger 11.. The very last stage of hammer plunger movement in this way swings the disconnector into'operation and releases the action bar. I-Iowtion. Instead, the, engagement is, at a minimum,

swing the disconnector into disconnecting posiarranged so that a rearward pull on the foreend I l will apply sufficient frictional force at the engagingfaces to prevent the disconnection from taking place until that rearward pull is relaxed. At a maximum, the surfaces may engage at such an angle that actual forward movement of the action bars is required before disconnection is possible. When the gun fires normally, such a relaxing or actual forward movement is involuntaryas the gun recoils relative to its support by the fore-end. In a misfire, or hangfire, this relationship prevents'unlockin the action involuntarily with the hazard of ahangfire exploding with an unlocked breech. When the disconnector has operated, the trigger will remain inoperative until the action has been again closed and completely locked with the action bar lock in its proper place. Thus, the trigger cannot be accidentally pulled to fire the shell as the breech is bein closed. Further, if the trigger is held back while the action is operated, the sear will retain the hammer until such time as the trigger has been released and the action bar lock engaged; The usual type of manually operable cross bolt safety 78 is also provided to positively block inadvertent trigger operation when the gun is carried loaded and locked. This fire control is as safe as possible in that it may be positively locked, cannot fire on an open breech, cannot fire a second shot without deliberately releasing, and cannot be involuntarily opened during a hangfire. Further, it will be noted that the sear and trigger are centrally pivoted and thus almost perfectly balanced with respect to jolts and jars from any direction. Substantially the only condition which could cause accidental firing if the gun were dropped or otherwise jarred with the safety oif would be an actual physical impact of the trigger upon some relatively fixed object.

Take-down This gunmay be taken down for cleaning or packing by simply removing the magazine cap and pulling the barrel and barrel extension forwardly out of the receiver. Obviously, in the case of the shooter who desires to useinterchangeably a long full choke barrel and a shorter open bored barrel, costs will be at a minimum. With most of the presently available types of takedown guns, it is necessary also to replace the magazine tube, fore-end, and action bar assembly.

The breech bolt and fore-end assembly may be readily removed for further cleaning or inspection by inserting the finger into the receiver from the bottom and manually depressing the left hand shell latch 44 to disengage the cam lug 49 thereon from the cut-away 50 in the left hand action bar 19. The fore-end, action bars, and breech bolt assembly may then be removed through the front of the receiver vacated by the previous removal of the barrel. The locking block may be lifted from the recess in the breech bolt, the bolt lifted from the breech bolt slide, and the slide disengaged from the interengaging notches in the action bars. Assembly of the breech bolt mechanism may be performed in the reverse order, it being noted, however, that it is necessary to manually depress the right hand shell latch 43 to clear the lug 48 from the path of the right hand action bar i 8 and, after a short further movement, to perform the same operation on the left hand shell latch 44. The assembly may then be completed by pulling rearwardly on the fore-end and the barrel replaced by reversal of the initial take-down operation. Although not ordinarily necessary for cleaning or inspection, the fire control assembly may be readily removed by pushing out the front and rear trigger plate pins and'removing the trigger plate from the bottom of the receiver.

Although a specific slide operated shotgun has been illustrated and described in detail, it will be obvious that features of our invention are applicable to other types of weapons. For example, the breech locking mechanism would function equally well if the slide were operated from a gas piston and the only other required change within the receiver would be to trim off the end of the action bar lock to permit its ready depression by rearward movement of the action bars. Similarly, the same breechlocking means could be utilized in a recoil operated gun by the simple expedient of coupling an action closing spring to the slide, as in the copending Crittendon application Serial Number 79,368, now Patent No. 2,570,772, previously referred to.

Accordingly, it is not intended that the invention be considered as limited to the specific construction shown, and reference may be made to the appended claims for a definition of the scope of our invention.

We claim:

1. In a firearm comprising a receiver, a barrel, and means defining a locking recess positioned in said receiver in fixed relationship to said barrel, the combination comprising a breech bolt slide supported for reciprocatory movement in said receiver and having thereon an upwardly proj ecting lug, a breech bolt supported on said breech bolt slide and .having extending vertically therethrough a slot defined by substantiall planar side and end Walls and adapted to receive said slide lug, the lengths of said slot and said lug respectively being such as to enable a limited longitudinal movement of said slide relative to said breech bolt, a tilting locking block vertically confined in said slot in operative relation to said lug solely by engagement between said lug and the surfaces of said receiver and locking recess defining means overlying said slot and laterally confined in said slot solely by engagement between said planar walls of said slot, spaced cam surfaces on the lower side of said locking block cooperating with said lug to tilt said locking block as an incident to the movement of said slide relative to said bolt, and a locking lug on said locking block adapted for interengagement with the said locking recess when said locking block is tilted by forward movement of said slide lug relative to said breech bolt.

2. The combination described in claim 1, said locking block being completely free from pivotal attachment at any point to either said breech bolt or said breech bolt slide.

3. Ilhe combination described in claim 1, the forward one of said planar end walls of the slot in said breech bolt being substantially perpendicular to the line of reciprocation of said breech bolt and breech bolt slide, the forward end of said locking block being shaped to present a substantially planar surface which is in facial engagement with the forward one of the end walls of said slot when said locking lug is received in said recess.

4. The combination described in claim 1, one of said cam surfaces comprising a downwardly and rearwardly facing breech bolt locking surface 10 formed near the front end of the lower surface of the locking block and adapted to cooperate with the forward edge of said slide lug to lift the front end of said locking block as the slide moves forward relative to the breech bolt.

5. The combination described in claim 4, the upper surface of said locking block behind the locking lug and between locations defined by vertical projections of said cam surfaces being formed to define a. fulcrum contacting the upper Wall of the receiver about which said locking block may rock in tilting within said aperture.

6. The combination described in claim 5, the other of said cam surfaces comprising a. downwardly and forwardly facing breech bolt unlocking surface formed near the rear end of the lower surface of the locking block and adapted to cooperate with the rear edge of said slide lug to lift the rear end of said locking blocl; as

the'slide moves rearward relative to: the breech cam surfaces being longitudinally spaced by a distance such that the slide lug must substantially disengage from one of said cam surfaces before it engages the other of said cam surfaces.

8. The combination described in claim 6, said breech bolt locking cam surface being spaced rearwardly from the front end of said locking block by a fiat portion of substantial area. beheath which a portion of the top surface of the slide lug may be positioned when the slide is in its foremost position relative to the breech bolt.

9. In a firearm comprising a're-ceiver and a barrel provided with a barrel extension projecting into said receiver and having therein a locking recess, the combination comprising a breech bolt slide supported for reciprocatory movement in said receiver and having thereon an upwardly projecting lug, a breech bolt supported on said breech bolt slide and having extending vertically therethrough a slot defined by substantially planar end and side walls and adapted to receive said slide lug, the lengths of said slot and said lug respectively being such as to enable a limited longitudinal movement of said slide relative to said breech bolt, a tilting locking block vertically confined in said slot in operative relation to said lug solely by engagement between said lug and the surfaces of said receiver and barrel extension overlying said slot and laterally confined in said slot solely by engagement between said planar walls of said slot, longitudinally spaced cam surfaces on the lower side of said locking block cooperating With said lug to tilt said looking block as an incident to the movement of said slide relative to said bolt, and a locking lug on said locking block adapted for interengagement with the said locking recess in said barrel extension when said locking block is tilted by forward movement of said slide lug relative to said breech bolt.

10. In a firearm comprising a. receiver and a takedown barrel provided with a barrel extension removably projecting into the receiver and having therein a locking recess, the combination comprising a breech bolt slide supported for reciprocatory movement in said receiver and having thereon an upwardly projecting lug, a breech bolt supported on said breech bolt slide and having extending vertically therethrough a slot defined by substantially planar side and end walls and adapted to receive said slide lug, the lengths.

11 of said slot and said lug respectively being such as to enable a limited longitudinal movement of said slide relative to said breech bolt, a tilting locking block vertically confined in said slot in operative relation to said lug solely by engagement between said lug and the surfaces of said receiver and barrel extension overlying said slot and laterally confined in said slot solely by engagement between said planar walls of said slot, cam surfaces on said locking block cooperating with said lug to tilt said locking block as an incident to the movement of said slide relative to said bolt, and a locking lug on said locking block adapted for interengagement with the locking recess in said barrel extension when said locking block is tilted by forward movement of said slide lug relative to said breech bolt, said breech bolt slide, breech bolt, and locking block being removable as a unit through the front end of said re- 12 eeiver when the'barrel and barrelextension'have been disassembled therefrom.

' LE-XEE R. 'CRITTENDON.

PHILIP R. HASKELL.

References Cited in the file "of this patent UNITED STATES PATENTS Number 'Name Date 4 577,281 Browning Feb. 16,1897

781,765 Browning Feb. '7, 1905 882,625 Catron Mar. 24, 1908 883,020 Hepburn Mar. 24, 1908 1,487,799 Pedersen Mar. 25, 1924 2,032,929 Garrison 1 Mar. 3, 1936 2,204,289 Williams June 11, 1940 2,345,077 Swebilius Mar. 28, 1944 2,418,946 Loomis Apr. 15, 1947 2,476,196 Humeston July 12, 1949 

